Forging method

ABSTRACT

A METHOD FOR FORMING FERROUS PARTS AT AN INTERMEDIATE TEMPERATURE BETWEEN NORMAL HOT FORGING AND COLD FORMING TEMPERATURES.

Jan-.25 19.71 J. E. cARDlLLo 3,557,587

" FORGING METHOD, i

Original Filed Oct. 23, 1965 l [M l United States Patent 1' hee 3,557,587 Patented Jan. 26, 1971 U.S. Cl. 72-41 27 Claims ABSTRACT OF TI-IE DISCLOSURE A method ffor forming ferrous parts at an intermediate temperature between normal hot forging and cold forming temperatures.

The present application is a divisional application based on the copending application of Jerry E. Cardillo, Ser. No. 503,400, filed Oct. 23, 1965 and which has issued into lU.S. Pat. fNo. 3,378,903 on Apr. 23, 1968.

The present invention relates to a method for forming parts at an intermediate temperature between normal hot forging and cold forming temperatures and to forming such parts from solid stock such as bar or wire. While scaling or oxidation of ferrous material will occur slowly at normal ambient temperatures, the rate of scaling increases with temperature.

'In hot forging parts from steel the material is initially heated to around 2000 F. and higher. Thus at hot forging temperatures a substantial scale and a significant amount of decarburization will occur. Since the scale and the decarburized surfaces must be removed, there is by nature of this process a certain amount of material wasted not to mention the cost of the scale removal operation. Parts can be made without scale, by cold forming; however, the material at normal ambient temperatures has higher strength characteristics and hence can be shaped only with substantially higher forces. Frequently this would necessitate more cold forming stages whereby the material can be formed to a desired shape gradually. In addition if the material is worked to any considerable extent over a series of operations then cold working can increase the strength of the part whereby the part must be annealed in between successive cold forming operations.

In the present invention the parts are formed while the material is at an intermediate temperature high enough to reduce the strength of the -material to facilitate forming and yet below the hot forging temperature at which scaling and decarburization occurs at a more rapid rate. It is an object of the present invention to provide a novel process for forming parts at a temperature below the normal-hot forging temperature at which the strength of material of the parts is substantially reduced while the formation of scale and the occurrence of decarburization is precluded to allow the manufacture of close tolerance forgings.

In the present invention a lubricant is utilized which will not vaporize at the intermediate temperature or at least will be on the part during the forming operation; the lubricant functions both to minimize scaling and decarburization and also to reduce the forces necessary to form the parts. By using the method of the present invention bar or wire stock can be utilized with a minimum amount of waste thereby providing for low material cost per part. Therefore, it is an object of the present invention to provide a novel method for forming parts at an intermediate temperature in which bar or wire stock can be utilized and in which a lubricant is utilized to minimize scaling and decarburization While decreasing friction.

The extent of scaling is based upon a temperature-time relationship. While scaling does occur more rapidly at higher than at lower temperatures, the extent of scaling can be minimized at higher temperatures by minimizing the time the material is maintained at that temperature. Therefore it is another object of the present invention to provide a novel method for forming parts at high temperatures with a minimum amount of scale.

|The present invention is specificially contemplated for used in the manufacture of annular parts such as bearing parts. Therefore, it is an object of the present invention to provide a new and improved method for manufacturing annular parts. It is a further object of the present invention to provide a new and improved method of manufacturing bearing races from bar or wire stock.

As a part of the present invention it is contemplated that more than one bearing race (or annular part) can be forged together as an integral forging. In this way inner and outer races could be forged together. Therefore, it is another object of the present invention to provide a novel method for manufacturing annular parts such as bearing races in which two or more parts are forged together.

The present invention also contemplates the integral forging of at least two races or annular parts. By slightly axially separating the races they can be machined together hence reducing the number of handling steps, reducing the amount of time required to machine a given number of races and hence resulting in a cost saving. Therefore, it is still another object of the present invention to provide a method for forging a plurality of bearing races as an integral member and machining the races, or parts, together while still integral.

The subject application is described and shown in conjunction with the manufacture of bearing races; it should beunderstood that while some of the features of the present invention may have particular utility in the manufacture of bearing races the scope of the present invention is not necessarily limited thereto.

Other objects, features, and advantages of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings, in which:

FIG. l depicts the solid wire or bar stock from which the parts can be made by means of the present invention;

FIG. 2 depicts a slug which has been sheared oli to a preselected size 'from the wire or bar stock of FIG. l;

FIG. 3 depicts the shape of the slug of FIG. 2 after it has been sized or formed into a workpiece;

FIG. 3A depicts the shape of a different shaped workpiece which has been sheared from bar stock and which, in a modified form of the process, can be used in place of the workpiece shown in FIG. 3;

FIG. 4 represents in block form two steps which are performed upon the workpieces of FIGS. 3 and 3A;

FIG. 5 depicts the workpieces of FIGS. 3 and 3A formed into a cup-shaped part after the heating step of FIG. 4,'

FIG. 6 depicts the cup-shaped part of FIG. 5 after having been machined to dene an inner and outer bearing race;

FIG. 7 is a sectional view of the inner and outer races of FIG. 6 after having been separated; and

FIG. 8 depicts the inner and outer races in a bearing assembly.

Looking now to the drawings, in FIG. l the bar or wire stock from which the articles are made by the process or method of the subject invention is shown to be of a solid cylindrical form and is generally indicated Aby the numeral 10. First a preselected volume of material is sheared to form a slug 12 as shown in FIG. 2. Next the slug 12 is sized by cold forming to t the subsequent die and as shown in FIG. 3 is formed into a solid cylindrically shaped workpiece generally indicated by the numeral 14. The workpiece 14 is then coated in a step indicated by the block designated with the numeral 16. The coating is provided to prevent oxidation or scaling and decarburization of the material of workpiece 14 which would occur at an accelerated rate at the high temperature subsequently involved; it is also desirable that this coating act as a lubricant in order to reduce the forces required to deform the workpiece 14. Since the slug is to be heated to a temperature at which the strength of the material is substantially reduced, the coatings selected are those which will not Vaporize at this temperature or at least will vaporize slowly enough so that after heating, subsequent operations can be made with the coating still adhering to the surface of the workpiece 14. In one form of the invention the workpiece 14 being made of steel is first coated with manganese phosphate which acts as a carrier for the application of a lubricant which is tungsten disulphide. After the coating step, the workpiece 14 is then heated by induction or other suitable apparatus and this stage is generally indicated by the block designated by the numeral 18. In this step the workpiece 14 is heated to a high temperature which in the preferred form is below the normal hot forging temperature of the material and yet is substantially above the ambient temperature and at a level at which the strength of the material is substantially reduced. In the case of steel, temperatures in the range of between 1300 and 1600" F. are preferred. For case and through hardening steels used in the manufacture of bearing rings, etc., l300 is the preferred ternperature since it is still below the hot forging temperature at which scaling and decarburization are aggravated and yet provides for a substantial reduction in the strength of the material of the workpiece 14. To obtain an appreciable reduction in the strength of steel the minimum temperature contemplated is approximately 1000 F. The heating of the workpiece 14 to the desired temperature is done as rapidly as possible; by doing this the material will be at elevated temperatures for only a short time and hence, even without the application of a protective coating, scaling will be kept to a minimum. The combination, of course, of the use of a protective coating plus rapid heating provides the best results with the least amount of scale and decarburization and with the least amount of resultant frictional force.

The workpiece 14 while in the heated condition is placed in a female die 20 which defines a pair of circular coaxially located cavity portions 22 and 24, the portion 22 being of a smaller diameter than the portion 24. A knock-out punch 26 is located at the bottom of the portion 22. The workpiece 14 is formed with a recess 15 which is of a size to receive the tip 27 of the knock-out 26 whereby the workpiece 1-4 is piloted in the cavity. With the workpiece thus located in the cavity a punch 28 having a preselected shape is caused to engage the workpiece 14 while at the elevated temperature whereby the cupshaped part 30 is formed in a single strike.

The part 30 as formed comprises a pair of generally annular ring portions 32 and 34 which correspond in outside diameter to the diameters of the cavity portions 22 and 24, respectively. The portions 32 and 34 are axially separated from each other and joined by a web 36. Offset from the bottom end of the smaller ring portion 32 is formed a fiat web 38. Note that the tip 27 extends partly within the die cavity thus resulting in a flow of material both forward and reverse to fill the cavity. By so moving the material good flow is obtained and folds are eliminated. Thus by offsetting the web 38 good flow characteristics are obtained; by locating the web 38 offset from the bottom end the minimum thickness of the web 38 can be reduced from that minimum thickness obtainable if the web were located at the very bottom. In order to maintain good die life and to preclude the attainment of excessive loads on the dies, it has been found that the web 38 should be limited in its minimum thickness. For example, for a part such as 30 made of a bearing steel and having a diameter of 1%6" 22 the web 38 should have an average yminimum thickness of approximately 1/8". Even at the elevated temperatures of the workpiece 14, attempts to reduce the metal in the web 38 to less than the average lz" thickness results in excessively high press loads. This average thickness will vary with different materials and with different sized parts. It would be impossible to set forth the minimum thickness for all combinations of materials and sizes; it is sufiicient that this limitation has been recognized and pointed out whereby now one skilled in the art could determine the minimum thickness for different combinations. It is also significant that the volume of material provided in workpieces 14 or 14a exceed by no more than ten percent the volume of the cavity defined by the die. If the volume exceeds ten percent the die loads increase to excessive levels. Thus the volume of the workpieces 14 and 14a should be controlled.

Note that the cup-shaped part 30 is obtained in one strike of the punch 28 from the workpiece 14. Under cold heading practices it would require several such strikes plus annealing and coating operations before a cup-shaped part such as the part 30 could be obtained from a workpiece such as workpiece 14. With the present invention even with larger or different parts in which more than one strike would be required the material could remain generally at the intermediate temperature for a time sufficient to permit additional strikes without reheating; of course, no intermediate annealing operation would be required. The number of strikes at the intermediate temperature still would be less than that required by cold forging and no intermediate anneal steps, as required by V cold working would be necessary. Such a shape (as part 30), however, might be obtained in one blow by means of conventional hot forging, i.e. heating the material up to approximately 2000 F.; however, in conventional hot forging processes scaling forms to a substantial degree and hence a greater amount of material would have to be used to dimensionally end up with the same sized part since the scale would have to be removed.

If necessary or desirable the heating can take place prior to forming the workpiece 14; no reheating would be required, since the next strike (shown in FIG. 5) could still be made prior to any substantial drop in material temperature. Also, rather than preforming a workpiece 14, a workpiece 14a (see FIG. 3A) could be used. Workpiece 14a can be sheared from bar stock having a diameter substantially equal to the diameter of the small diameter cavity portion 22. The workpiece 14a will -then be automatically piloted in the die; note that no -sizing operation is required and workpiece 14a is used 1n the form as it is sheared from the bar stock.

With the two annular portions 32 and 34 connected together, the piece 30 can be machined together and assuming now that the ring portion 32 is to be the inner race of a ball bearing and the ring portion 34 is to be the outer race of the ball bearing, then the cup-shaped part 30 will be machined to a shape as shown in FIG. 6. Note that the web 38 has been removed. Looking at FIG. 6, portions similar to like portions of the cup-shaped part 30 in FIG. 5 have been given the same numerical designation with the addition of the letter subscript a. Thus the machine cup-shaped part 30a then will have its large diameter ring portion 34a with an inner raceway 40 machined therein and the small diameter ring portion 32a will have a raccway 42 formed on its outer surface. At the completion of this machining operation, the portions 32a and 34a can be separated by cutting away the connecting web portion 36a. Upon removal of the web 36a, a large diameter ring portion 34a defines an outer race member and the small diameter ring portion 32a defines an inner race member (see FIG. 7) which can then be assembled with a plurality of balls indicated by for the small diameter portion the numeral 44 to form thereby a ball bearing assembly 46.

Note that while the specific embodiment shown is for the manufacture of ball bearing races, it should be understood that the present invention is equally applicable to the manufacture of other type bearing races including straight, tapered roller bearings and any type of annular rolling element type bearings.

Note then in this process that the inner and outer races can be machined separately or together. At the same time because of the close tolerances obtained by this process, the rings 32a and 34a need be machined only selectively, i.e., as to form raceways, chamfers, etc. For some bearing constructions the machining of raceways can be eliminated. The parts are now ready for hardening and grinding before assembly as shown in FIG. 8. It can be appreciated that instead of forming inner and outer bearing races for the same bearing assembly, inner and outer races for different bearing assemblies can be simultaneously formed together and machined dually. Likewise, two outer or two inner races for different bearing assemblies could be formed together and machined dually.

Looking back to FIG. 5, note that the ring portions 32 and 34 are axially offset from each other by means of the web 36. By providing such an offset structure, it has been found that the simple workpieces 14 and 14a can be utilized whereby the cup-shaped member 30 can be formed in one step or for large sizes in a minimum number of steps (less than that required by cold forming). In such an offset structure good ow characteristics are obtained and the part can be formed without folds or cracks. In addition, by so offsetting the portions 32 and 34, the dual machining of the two portions can be facilitated. If the two portions were nested it can be appreciated that dual machining would be impossible. However, by nesting the parts the loss of material in web 36 would be eliminated; therefore, in some applications a nested forging would be desirable.

As previously noted, by rst applying a protective coating prior to heating the workpiece 14 up to the forming temperature, scaling and decarburization will be prevented. Scaling and decarburization will occur, of course, with a steel part at substantially any temperature, with the rate of scaling and decarburization, however, generally increasing with an increase in temperature. Hence the selection of the coating will in part, at least, depend upon the temperature to which the part is heated and upon its cooling time. In the present invention it is con-.

templated that heating will be done by induction or other rapid means and with the forming being performed quickly thereafter such that the part will be at the high temperature for only -a short period. Thus the coating is selected to be such that it will not completely vaporize during the time interval between heating and forming after coating. Alternatively, the heating of the workpieces can be done in a controlled atmosphere in which scaling and decarburization will not occur. It is also desirable that some lubrication be provided between the die and the workpiece 14. Thus a coating which has lubricity characteristics as well as one which prevents scaling can be selected. The manganese phosphate tungsten disulphide coating previously discussed will serve the dual coatinglubricating function. Note that in lieu of applying a lubricant to the workpiece 14, a lubricant can be applied t the components of the die which contact the workpiece 14.

In working with steel, it is significant that some steels, Le., high carbon, upon once being heated to the critical temperature, will harden upon cooling in air. When such materials are thus hardened, it is necessary to then perform a spheroidizing anneal operation to facilitate subsequent machining. The temperature at which this will occur for that material is normally referred to as the critical temperature. In the present invention, in order to avoid the necessity for a subsequent annealing operation, the part is heated to a temperature below the critical temperature of the material.

While it will be apparent that the preferred embodiments of the invention disclosed are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

1. The method of forming a close tolerance part from a ferrous material by deforming a workpiece in the form of a solid slug of material, comprising the steps of: heating the workpiece to a preselected temperature at which the strength of the material of the workpiece is substantially reduced from its strength at ambient temperature but below the critical temperature of the material at which air hardening occurs, locating the workpiece in a female die member, forging the workpiece by engaging it with a male die member while at said preselected temperature to form the part, and maintaining a protective coating on said workpiece while at said preselected temperature and during said deforming to prevent scaling and decarburization whereby said part is a close tolerance part requiring minimum machining, said preselected temperature being in excess of about 1000 F.

2. The method of claim 1 including maintaining on said workpiece a coating having lubricating characteristics prior to and during deforming to facilitate deformation of the workpiece.

3. The method of claim 1 for forming a pair of annular members with said workpiece initially being a solid slug of material having a predetermined height and a predetermined general diameter and with said steps including deforming said workpiece while at said preselected temperature into an intermediate part, having a generally circular shape and having a thickness substantially reduced relative to said height and having a diameter substantially greater than said predetermined general diameter.

4. The method of claim 3 with said steps including forming from said intermediate part a pair of annular members with the substantially greater diameter being approximately the finished diameter of one of said annular members.

5. The method of forming a close tolerance part by deforming a solid slug of ferrous material comprising the steps of: deforming the slug to form a sized workpiece having a preselected shape, having the workpiece at a preselected temperature at which the strength of the material is substantially reduced from its strength at ambient temperature but below the critical temperature of the material at which air hardening occurs, locating the workpiece in a female die member, forging the workpiece by engaging it with a male die member while at said preselected temperature to form the part, and maintaining a protective coating on the workpiece while at said preselected temperature to prevent scaling and decarburization of its material at said preselected temperature whereby a close tolerance forging requiring a minimum of machining can be made, said preselected temperature being in excess of 1000 F.

`6. The method of forming a close tolerance, cup-shaped part by deforming a slug of ferrous material comprising the steps of: deforming the slug to form a sized workpiece having a preselected shape, having the workpiece at a preselected temperature at which the strength of the material is substantially reduced from its strength at ambient temperature but below the critical temperature of the material at which air hardening occurs, locating the workpiece in a female die member, forging the workpiece by engaging it with a male die member while at said preselected temperature in a single blow into the cup-shaped part, and maintaining a protective coating on the workpiece while at said preselected temperature to prevent scaling and decarburization of its material at said preselected temperature, said preselected temperature lbeing in excess of 1000o F.

7. The method of forming a part by deforming a workpiece made of a ferrous material comprising the steps of: heating the workpiece to a preselected temperature in the range of from about l300 F. to about 1600 F., deformthe workpiece by forging while at said preselected temperature to form the part, and maintaining a protective coating on said workpiece through said heating and deforming steps to prevent scaling.

8. The method of forming a cup-shaped part by deforming a slug of ferrous material comprising the steps of: deforming the slug to form a sized workpiece having a cylindrical shape, having the workpiece at a preselected temperature at which the strength of the material is substantially reduced from its strength at ambient temperature but below the critical temperature of the material at which air hardening occurs, and deforming the workpiece by forging while at said preselected temperature in a single blow into the cup-shaped part, said preselected temperature being greater than around 1000 F.

9. The method of forming a cup-shaped part by deforming a slug of ferrous material comprising the steps of: deforming the slug to form a sized workpiece having a cylindrical shape, having the workpiece at a preselected temperature at which the strength of the material is substantially reduced from its strength at ambient temperature but below the critical temperature of the material at which air hardening occurs, locating the workpiece in a die having a pair of axially offset cavity portions, deforming the workpiece by forging while at said preselected temperature in a single blow into the cup-shaped part having a pair of axially separted ring portions connected together by a web, said preselected temperature being greater than around 1000 F.

10. The method of forming a pair of annular members from a ferrous material by deforming a solid workpiece comprising the steps of having the workpiece at a preselected temperature at which the strength of the material is substantially reduced from ambient but below the critical temperature at which air hardening occurs, locating the workpiece in a female die member, forging the workpiece by engaging it with a male die member while at said preselected temperature to form a part defining a pair of ring portions with the ring portions dening the pair of annular members, separating said ring portions, and maintaining a protective coating on the workpiece while at said preselected temperature to prevent scaling and decarburization, said preselected temperature being greater than around 1000 F.

11. The method of claim 7 with said workpiece being a at plate-shaped part and including the step of removing a center slug to define one of the annular parts.

12. The method of forming a part from a ferrous material by deforming a workpiece comprising the steps of: heating the workpiece to a preselected temperature at which the strength of the material of the workpiece is substantially reduced from its strength at ambient temperature, said temperature being in the range of from about 1000 F. to the critical temperature at which hardening occurs from air cooling and below the temperature at which excessive scaling occurs, locating the workpiece in a female die member, forging the workpiece by engaging it with a male die member while at said preselected temperature to form the part, and maintaining a protective coating on said workpiece while at said preselected temperature to prevent scaling and decarburization allowing close tolerance forgings.

13. The method of forming a cup-shaped part by deforming a slug of ferrous material comprising the steps of: deforming the slug to form a sized workpiece having a preselected shape, having the workpiece at a preselected temperature at which the strength of the material is substantially reduced from its strength at ambient temperature but below the critical temperature of the material at which air hardening occurs, locating the workpiece in a female die member, forging the workpiece by engaging it with a male die member while at said preselected temperature into the cup-shaped part While maintaining a web at a preselected position internally of the cup-shaped part at a preselected average thickness no less than a predetermined minimum thickness less than which the deforming forces become execessive, rnaintaining a protective coating on the workpiece while at said preselected temperature to prevent scaling and decarburization of its material at said preselected temperature, said preselected temperature being greater than around 1000 F.

14. The method of claim 13 in which, for a part having a diameter of around 1%6 adjacent the web, said minimum thickness is approximately ls".

15. The method of forming a close tolerance part of ferrous material by deforming a workpiece comprising the steps of: heating the workpiece to a preselected temperature at which the strength of the material of the workpiece is substantially reduced from its strength at ambient temperature but below the critical temperature of the material at which air hardening occurs, locating the workpiece in a female die member, forging the workpiece by engaging it wtih a male die member while at said preselected temperature to form the part, and maintaining a protective coating on said workpiece while at said preselected temperature to prevent scaling and decarburization, said coating having lubricating characteristics to facilitate the deformation of the workpiece and said preselected temperature being greater than around 1000 F.

16. The method of forming a close tolerance part of ferrous material by deforming a workpiece comprising the steps of: heating the workpiece to a preselected ternperature at which the strength of the material of the workpiece is substantially reduced from its strength at ambient temperature but below the critical temperature of the material at which air hardening occurs, locating the workpiece in a female die member, forging the workpiece in a minimum number of blows by engaging it with at least one male die member while at said preselected temperature to form the part with the blows being uninterrupted by intervening process steps, said preselected temperature being greater than around 1000 F.

17. The method of forming a close tolerance part of ferrous material by deforming a workpiece comprising the steps of: heating the workpiece to a preselected tem perature at which the strength of the material of the workpiece is substantially reduced from its strength at ambient temperature but below the critical temperature of the material at which air hardening occurs, locating the workpiece in a female die member, forging the workpiece in a minimum number of blows by engaging it with at least one male die member while at said preselected temperature to form the part with the blows being uninterrupted by intervening process steps, and maintaining a protective coating on said workpiece while at said preselected temperature to prevent scaling and decarburization, said preselected temperature being greater than around 1000 F.

18. The method of forming a close tolerance part of ferrous material by deforming a solid slug comprising the steps of: deforming the slug to form a sized workpiece having a preselected shape, locating the workpiece in a female die member, forging the workpiece by engaging it with a male die member while it is at a preselected temperature at which the strength of the material is substantially reduced from its strength at ambient temperature but below the critical temperature of the material at which air hardening occurs, and applying a protective coating to the workpiece prior to the heating to said preselected ternperature to prevent scaling and decarburization of its material at said preselected temperature, said preselected temperature being greater than around 1000 F.

19. The method of forming a cup-shaped part by deforming a slug comprising the steps of: deforming the slug to form a sized workpiece having a preselected shape,

locating the workpiece in a female die member, forging the workpiece by engaging it with a male die member while it is at a preselected temperature at which the strength of the material is substantially reduced from its strength at ambient temperature in a minimum number of blows into the cup-shaped part, said preselected temperature being below the temperature of the material at which air hardening occurs and maintaining a protective coating on the workpiece while at said preselected temperature to prevent scaling and decarburization of its material at said preselected temperature, said preselected temperature being greater than around 1000 F.

2,0. The method of forming a cup-shaped part by deforming a slug of ferrous material comprising the steps of: providing a slug from stock to have a flat plate shape being of a size to pilot itself in a die, having the slug at a preselected temperature at which the strength of the material is substantially reduced from its strength at ambient temperature but below the critical temperature of the material at which air hardening occurs, and forging the slug by engaging it with a male die member while at said preselected temperature in a single blow into the cup-shaped part, said preselected temperature being greater than around 1000" F.

21. The method of forming a cup-shaped part by deforming a slug of ferrous material in a die having a pair of coaxial cavity portions, comprising the steps of: providing a slug from stock to have a flat plate shape being of a size to pilot itself in the smaller cavity portion of the die, having the slug at a preselected temperature at which the strength of the material is substantially reduced from its strength at ambient temperature but below the critical temperature of the material at which air hardening occurs, locating the workpiece in the die, forging the workpiece by engaging it with a male die member while at said preselected temperature into the cup-shaped part, said preselected temperature being greater than around l000 F.

22. The method of forming a cup-shaped part by deforming a slug of ferrous material in a die having a pair of coaxial cavity portions, comprising the steps of: deforming the slug to form a sized workpiece having a cylindrical shape with a piloting cavity at one end, having the slug at a preselected temperature at which the strength of the material is substantially reduced from its strength at ambient temperature but below the critical temperature of the material at which air hardening occurs, piloting the workpiece in the die with the piloting cavity located upon a punch, forging the workpiece by engaging it with a male die member while at said preselected temperature, said preselected temperature being greater than around 1000 F.

23. The method of forming a cup-shaped part from a ferrous material by deforming a workpiece comprising the steps of: heating the workpiece to a preselected temperature at which the strength of the material is substantially reduced from its strength at ambient temperature but below the critical temperature of the material at which air hardening occurs, locating the workpiece in a female die member, forging the workpiece by engaging it with a CTI male die member while at said preselected temperature into the cup-shaped part while maintaining a web intermediate its ends, said preselected temperature being greater than around l000 F.

24. The method of forming a cup-shaped part by deforming a workpiece of a ferrous material comprising the steps of heating the workpiece to a preselected temperature at which the strength of the material is substantially reduced from its strength at ambient temperature but below the critical temperature of the material at which air hardening occurs, locating the workpiece in a female die member, forging the workpiece by engaging it with a male die member while at said preselected temperature into the cup-shaped part while maintaining a web intermediate its ends, maintaining a protective coating on the workpiece while at said preselected temperature to prevent scaling and decarburization of its material at said preselected temperature, said preselected temperature being greater than around 1000 F.

25. The method of claim 1 with said preselected temperature being less than around 1600" F.

26. The method of forming a part from a ferrous material by deforming a workpiece comprising the steps of heating the workpiece to a preselected temperature at which the strength of the material of the workpiece is substantially reduced from its strength at ambient temperature, deforming the workpiece while at said preselected temperature to form the part, and maintaining a protective coating on said workpiece while at said preselected tempertaure and during said deforming to prevent scaling and decarburization and including maintaining on said workpiece a coating having lubricating characteristics prior to and during deforming to facilitate deformation of the workpiece.

27. The method of forming a part by deforming a solid slug of ferrous material comprising the steps of: deforming the slug to form a sized workpiece having a preselected shape, having the workpiece at a preselected temperature at which the strength of the material is substantially reduced from its strength at ambient temperature, deforming the workpiece while at said preselected temperature t0 form the part, and maintaining a protective coating on the workpiece while at said preselected temperature to prevent scaling and decarburization of its material at said preseelcted temperature whereby a close tolerance forging can be made.

lReferences Cited UNITED STATES PATENTS 1,345,045 6/ 1920 Waters 72--364 2,788,301 4/1957 Moore et al. 72-46 2,994,952 8/ 1961 Klooz 72-364 3,066,408 12/ 1962 Fader 72-364 3,096,579 7/ 1963 Waller 72-41 LOWELL A. LARSON, Primary Examiner U.S. Cl. X.R. 72--46, 364 

